This patch refactors the stxsdx instruction.  Reusable code is
extracted into a macro which will be used in subsequent patches
in this series.
Signed-off-by: NTom Musta <tommusta@gmail.com>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NAlexander Graf <agraf@suse.de>